Accurate assessment of radiation exposure doses and injury soon after exposure is critical for use in predicting short and long term health consequences. We intend to evaluate accidentally exposed workers by a variety of laboratory techniques. Specifically, analytical techniques will be used to quantitate internal radiation exposure dose using whole body counting and biologic effects by genetic analysis. For the latter, blood samples will be collected and used to evaluate for presence of chromosome aberrations and abnormalities in DNA repair. Standard health evaluation will include history, physical examination and clinical laboratory determinations. using a combination of indicators of exposure, and biological and health effects, our study should provide reliable information for evaluation of short and lnog term health risks.